Prof. Michael Oelze
University of Illinois
Dept. of Electrical and Computer Engineering
In conventional ultrasonic imaging, contrast between diseased and healthy tissues is often low because acoustic impedance differences between various tissues are small. Quantitative ultrasound (QUS) techniques have been used to increase the contrast between healthy and diseased tissues in ultrasonic imaging. Specifically, statistically significant differences between healthy and diseased tissues have been observed in preliminary studies from rodent models of breast cancer using high-frequency QUS imaging (i.e., > 10 MHz), whereas, these differences were not observed in conventional ultrasonic imaging. In these studies, QUS made use of estimates of effective scatterer diameter (ESD) and effective acoustic concentration (EAC) from the ultrasonic backscattered power spectra and the ratio of coherent to incoherent signal energy (k parameter) from the envelope statistics. In each of these cases, the contrast in QUS images was due to both microstructural differences and impedance differences between tissues. These techniques have also been applied to the monitoring of temperature elevations induced in samples and tissues for therapeutics. High-frequency QUS was observed to be sensitive to temperature changes in tissues and was robust against tissue motion. Assessment of thermal therapy was also conducted using high-frequency QUS and it was observed that QUS could quantify thermal injury. Improvements in modeling, identification of scattering sources responsible for scattering, multiparameter analysis, and signal processing techniques have led to further improvements in QUS techniques. Some of these improvements and latest developments in QUS techniques will be discussed.